Centrifugal Pump - Pump Power And Electrical Consumption

Hi,

Currently, we are asked to calculate power consumption in kWh for specific pumps in order to lay out a plan to be more energy efficient. 

I have started with the pump curve attached. The pump is used for NGLs with the original operating point at 620 GPM, 5200 ft of head and 76% efficiency (around 600 BHP) - Red Cloud. Electrical consumption has been calculated as follows:

Power = 600 BHP = 450 kW

E Consumption = 600 BHP x 0.75 x 1.1 x 24h/day = 11,880 kWh/day

The factor 1.1 is to account for electrical motor and parts losses

Currently the pump is running at 400 GPM with corresponding 500 BHP and around 65% efficiency (blue cloud).

Power = 500 BHP = 375 kW

E consumption = 500 BHP x 0.75 x 1.1 x 24h/day = 9,900 kWh/day

My understanding is that, as per pump affinity laws, power is proportional to the flowrate cube. Is that a correct approach? Electrical motor is a single speed motor (3560 RPM)

Thanks in advance

Sherif

Hi,

yes you are correct about affinity law :

https://www.engineer...laws-d_408.html

you may be interested with the excel sheet attached I did a few years ago. 

Breizh 

Thanks for the feedback Breizh

I found out that to estimate the actual power consumed by the motor, we simply use the equation P = V (volts) x I (amps) x SQRT(3) and this is for 3-phase motors. The efficiency of the motor and its parts will be equal to BHP (pump) / Inlet Power.

What do you think?

Hi,

P=U*I*3^.5*cos (phi) .

Consider your search engine for the definition of the different terms .

Note : Useful equipment and cheap is a Power Clamp meter , no need to measure other parameters (U,I ,Cos (phi)).

For the efficiency , you may find data from manufacturer's pumps curves.

Good Luck

Breizh 

Edited by breizh, 20 October 2020 - 05:13 AM.